To me, this usage is not too surprising. In French, we commonly say, for example, that a path is "praticable" meaning that it can be crossed.

To add to the first comment, the TLFi has, somewhere far down in the entry:

B. MAR. Libre pratique. ,,Autorisation d'entrer au port donnée à un navire ayant une patente de santé nette`` (LE CLÈRE 1960). Les matelots (...) subirent longtemps toutes les interrogations du bureau de Santé (...) et enfin nous fûmes admis en libre pratique à huit heures (STENDHAL, Mém. touriste, t.2, 1838, p.404).

I first came across the term in the diary of Captain Augustus Hervey, RN, a notorious rake of the 18th century, published as "Augustus Hervey: A Naval Casanova." A very entertaining read, illuminating the cosmopolitan lifestyle of the 18th century European nobility. There are many references to pratique as Captain Hervey's ship puts into various Mediterranean ports during the 1750s.

I take it the English phrase "sharp practice", which is still current, represents a survival of early businessy meanings of the noun.